Open to opportunities

Julian Au

@julianau

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Senior full-stack engineer building React/Next.js, Node.js, and healthcare interoperability products.

Zimbabwe

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What I'm looking for

I’m looking for freelance work where I can build and scale React/Next.js and Node.js/NestJS systems, including healthcare interoperability (FHIR/EHR/EMR) and AWS cloud architecture, with a strong engineering culture and measurable performance goals.

I’m a Senior Full Stack Engineer with 8+ years building production React, Next.js, Node.js, NestJS, and React Native applications scaled to 1M+ users. I deliver end-to-end systems with full-stack TypeScript throughout—architecture, implementation, and performance.

I specialize in the modern JavaScript/TypeScript stack: React 18/19, Next.js 14 App Router, Node.js, NestJS, Express.js, and Prisma ORM. On mobile, I build with React Native and Expo for iOS and Android, using offline-first patterns and secure local storage.

Healthcare interoperability is a core strength of mine. I’ve built HL7 FHIR R4 APIs and resource modeling, integrated EHR/EMR systems (Epic, Cerner) over FHIR and HL7 v2, and implemented SMART on FHIR authorization (OAuth 2.0 / OpenID Connect) with scoped, least-privilege access.

I also bring production AI/LLM experience—integrating OpenAI and Anthropic Claude, designing RAG pipelines with pgvector/Pinecone, and achieving measurable wins like 40% inference cost reduction and 55% latency improvement. I’m available for freelance React/Next.js development, FHIR/EHR/EMR engagements, Node.js/NestJS backend APIs, and AWS cloud architecture.

Experience

Work history, roles, and key accomplishments

Current

Full Stack Engineer

Current

Mascotte.AI

Nov 2024 - Present (1 year 8 months)

Built and owned architecture for an AI agent SaaS, including real-time voice pipelines and an end-to-end React/Next.js and Node.js backend platform. Implemented multi-tenant design, integrations (Stripe/PayPal, OAuth), real-time media/avatars, and developer platform tooling.

Next.js React TypeScript Node.Js Development Prisma MySQL AWS RDS WebRTC LLM TTS OpenRouter Deepgram ElevenLabs Google Cloud TTS LiveKit Pgvector React three fiber Arcware Pixel Streaming OAuth Pusher Socket.IO Webhooks

Senior Full Stack Engineer

VulnCheck

Jan 2024 - Sep 2024 (8 months)

Built a healthcare interoperability platform using NestJS/Node.js and Next.js/React, scaling to 1M+ active users with improved latency and throughput. Implemented HL7 FHIR R4 APIs, SMART on FHIR authorization, HL7 v2 interface engines, mobile offline-first sync, and AWS-based infrastructure and reliability controls.

Senior Full Stack Developer

Mercury Dasha

Sep 2022 - Dec 2023 (1 year 3 months)

Contributed to NestJS and React/React Native delivery with strong CI test/coverage practices and TypeScript rigor. Integrated OpenAI GPT and embeddings into search/recommendation flows and built an Expo mobile app with offline-first data sync and push notifications.

NestJS React React Native MongoDB Jest React Testing Library ESLint TypeScript CI Data Text Embedding Ada 002 Expo WatermelonDB APNS Heroku AWS Infrastructure

Full Stack & Mobile Developer

PXN Phantom Network

Mar 2019 - Jul 2022 (3 years 4 months)

Delivered production features across a high-traffic platform using Next.js, Django REST, PostgreSQL, and AWS, with strong automated testing to prevent regressions. Built and shipped LLM-powered features and a mobile app, and supported a migration from a PHP monolith to a TypeScript/Next.js + Django REST architecture.

Next.js React Django REST Framework PostgreSQL AWS Jest React Testing Library Expo React Native Swift Kotlin Expo Config Plugin TypeScript WebGL WebGL Marketing

Freelance Full Stack Developer

Independent

Jun 2017 - Feb 2019 (1 year 8 months)

Delivered end-to-end web and mobile freelance projects, owning scoping, estimation, build, and handoff across Node.js/React and React Native/Expo stacks. Built client-facing integrations including REST APIs, React component libraries, and payment/email functionality.

Node React React Native Expo MongoDB PostgreSQL Stripe PayPal REST APIs Component Libraries Email Automation

Junior Web Developer

Local Web Studio

Feb 2015 - May 2017 (2 years 3 months)

Built responsive marketing sites and small web applications using PHP and JavaScript tooling, then added backend modules with Node.js/Express and MongoDB. Developed internal CMS capabilities including database work, REST API design, and JWT authentication, while writing unit tests and fixing production bugs.